It is well known that the ventilator is an apparatus that can substitute for, control or change human normal physiological respiration, to increase the pulmonary ventilation volume, improve the respiratory function, decrease breathing power consumption and save the cardiac reserve ability. Such ventilator has become an important instrument for clinically salvaging and treating various respiratory failures as well as providing post-anesthesia and postoperative respiratory support. Ventilators include a pneumatic and electrically controlled ventilator, a pneumatic and pneumatically controlled ventilator, and an electric and electrically controlled ventilator, in terms of their control manners.
Presently, high-pressure gas is generally used by common pneumatic and electrically controlled ventilators as a driving gas source. In flow proportional valves used by most existing pneumatic and electrically controlled ventilators, an actuating element controlled by a voice coil motor is used to compress an elastic element to cause a linear displacement of the elastic element, which alters a throttle area of a fluid passage, thereby controlling the gas flow. However, an opening area of such proportional valve (i.e., a drift diameter) is relatively small, therefore the output pressure of the driving gas source is generally high in order to meet a flow requirement needed by the pneumatic and electrically controlled ventilator, as a result, the applicability of the pneumatic and electrically controlled ventilator is limited to locations, such as a hospital, where the required sufficient high-pressure driving gas source can be offered.
However, with the increasingly extended applicability of ventilators, the traditional pneumatic and electrically controlled ventilator cannot meet some usage requirements for the ventilator in some specific environment due to its excessive usage limitations. For example, when the ventilator is used for salvage in some place, such as outdoors, where a high-pressure driving gas source is insufficient or even unavailable, it is difficult to provide a steady and sufficient high-pressure driving gas source to the ventilator, thus the pneumatic and electrically controlled ventilator cannot provide a satisfying flow and therefore cannot work normally. In this case, the electric and electrically controlled ventilator, which uses only oxygen as a gas source and needs no high-pressure gas source, is usually used to supply gas to a patient under the standard atmosphere.
The electric and electrically controlled ventilator generally adopts a low-pressure gas source provided by a turbine as the driving gas source. However, since the turbine has a low trigger sensitivity and long inspiration response time, the electric and electrically controlled ventilator sometimes cannot be well synchronous with the breathing of a patient. The reason is that, when the low-pressure driving gas source is adopted, a flow proportional valve used by the electric and electrically controlled ventilator has a relatively small drift diameter, and the electric and electrically controlled ventilator can adopt only such a manner that its gas flow is controlled through directly controlling the rotate speed of the turbine. However, since a response speed of the turbine is not fast enough, the service life of the turbine would be affected by frequent acceleration and deceleration for long time of the turbine, thus the application of the electric and electrically controlled ventilator is also restricted.